Are Late Nights Making You Fat?

Night owls — even young ones — are far more likely than early birds to develop diabetes and other metabolic problems.

People who stay up late — whether they are shift workers or night owls — are likelier to develop diabetes, metabolic syndrome and muscle loss than their daytime counterparts, even when they get the same amount of sleep.

Ben Franklin's quote, “Early to bed, early to rise makes a man healthy, wealthy and wise,” appears to be right on the money, according to a recent study.

Men who were late night types were more likely to have diabetes than early risers; while the women night owls tended to have more belly fat and a great risk of metabolic syndrome.

“Regardless of lifestyle, people who stayed up late faced a higher risk of developing health problems like diabetes or reduced muscle mass than those who were early risers,” study co-author, Nan Hee Kim, said in a statement.

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“This could be caused by night owls' tendency to have poorer sleep quality and to engage in unhealthy behaviors like smoking, late-night eating and a sedentary lifestyle.”

Based on their answers to a questionnaire about their sleep-wake cycle, people in the study were classed as morning chronotypes, evening chronotypes or intermediate. A person's chronotype describes what part of the day they are normally most physically and mentally active.

Even though the night owls or evening chronotypes in the study tended to be younger, they had higher levels of body fat and triglycerides, or fats in the blood, than morning chronotypes did. They were also more likely to have sarcopenia, a condition where the body gradually loses muscle mass.

Men who were evening chronotypes were more likely to have diabetes than early risers, while the women night owls tended to have more belly fat and a great risk of Metabolic Syndrome, a cluster of risk factors that raises the risk of heart disease, stroke and diabetes.

Shift work has previously been linked to an increased risk of diabetes.

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Along with the questionnaire on sleeping habits and activity, the roughly 1,600 Koreans, aged 47 to 59, involved in the study furnished blood samples and underwent DEXA (dual X-ray) scans to measure total body fat and lean mass, and CT scans to measure abdominal or belly fat. Over a quarter (480) of the participants were classified as morning people, 95 as evening people, and the rest fell somewhere in between.

The fact that so many night owls were younger suggests an important health risk that needs to be addressed, according to Kim, a doctor in the Department of Internal Medicine at Korea University College of Medicine in Ansan, Korea. So many young people stay out late, and it's a long-term health risk they may not be aware they are taking.